1. Field of the Invention
The present invention relates to an electronic component, such as a multilayer ceramic capacitor, and to an electronic component built-in substrate. More specifically, the present invention relates to an electronic component that includes an outer surface on which a plurality of external terminal electrodes is provided and to an electronic component built-in substrate having a portion electrically connected to the external terminal electrodes.
2. Description of the Related Art
Various electronic devices, including mobile phones and portable music players, are becoming smaller and thinner through the years. In keeping with the trend, wiring substrates mounted on electronic devices and electronic components mounted on wiring substrates are also becoming smaller, and additionally, denser. To advance further miniaturization, an electronic component built-in substrate is being developed.
In an electronic component built-in substrate, an electronic component is embedded in a wiring substrate in advance. It is necessary to electrically connect an embedded electronic component to wiring of a wiring substrate. There are many ways for such electrical connection.
One example of an electrical connection method is described in Japanese Unexamined Patent Application Publication No. 2003-309373. First, an electronic component is embedded in a wiring substrate. Then, a via hole is formed by radiation of a laser beam from the wiring substrate while being aimed at an external terminal electrode of the internal electronic component. The inside of the via hole is filled with a conductive material to electrically connect the wiring of the wiring substrate and the external terminal electrode.
FIG. 12 is a schematic plan view for use in describing a known via-hole formation method using a laser beam. Here, only a top surface of an electronic component embedded in a wiring substrate is illustrated. An electronic component 101 illustrated in FIG. 12 includes a first external terminal electrode 102 and a second external terminal electrode 103 formed on a top surface 101a. A wiring substrate portion lies in the neighboring regions of the electronic component 101.
The first and second external terminal electrodes 102 and 103 are covered with a substrate layer of the wiring substrate. With the electrical connection method described in the above patent document, a laser beam is emitted from the substrate side to form a via hole for use in exposing the first external terminal electrode 102 or a via hole for use in exposing the second external terminal electrode 103. The external terminal electrodes 102 and 103 are made from a metallic plating film that reflects a laser beam, for example, a copper plating film. If an outer surface of the electronic component 101 other than a portion where the external terminal electrodes 102 and 103 are formed, for example, an outer surface in a gap region G between the external terminal electrodes 102 and 103, is radiated with a laser beam, the electronic component 101 is damaged.
As illustrated in FIG. 12, to radiate each of the external terminal electrodes 102 and 103 with a laser beam, it is necessary to avoid the radiation region of the laser beam from reaching the gap region G. A laser beam has straightness. When the external terminal electrodes 102 and 103 are radiated with a laser beam such that the laser beam is substantially perpendicular to the external terminal electrodes 102 and 103, the radiation region is substantially circular. Accordingly, as illustrated in FIG. 12, each of the regions A indicated by the broken lines in contact with the gap region G is the maximum permissible laser radiation region. In other words, it is necessary to emit a laser beam so as to fall within the substantially circular region indicated by the broken line.
The diameter of the substantially circular region indicated by the broken line is (L−g)/2, where L is the dimension of the electronic component 101 in the longitudinal direction and g is the dimension thereof in the width direction, and this value is the upper limit. Because of this, with the known electronic component 101, it is necessary to precisely emit a laser beam for use in forming a via hole, so tolerance for control of the position of the radiation region is low.